1. Field of the Invention
The present invention relates to a breather system for a fuel tank, and more particularly to a breather system for a fuel tank for supplying fuel to an engine of an engine-driven working machine.
2. Description of the Related Art
A fuel tank for supplying fuel to an engine of an engine-driven working machine, generally comprises a breather system for performing breathing action between the outside and an air chamber provided in an upper portion of the fuel tank in order to maintain a constant pressure in the fuel tank.
In a conventional breather system, as disclosed in Japanese Utility Model Application Laid-open No. 62-196791, a breather cap 2 is mounted on one side of an upper wall of a fuel tank 1 apart from a fuel supply port of the fuel tank 1; a breather chamber is formed within the breather cap 2 to communicate with an air chamber in an upper portion of the fuel tank 1; and a breather pipe opening into the atmosphere is provided to communicate with the breather chamber, thereby performing breathing action between the inside of the fuel tank and the atmosphere.
In the breather system disclosed in Japanese Utility Model Application Laid-open No. 62-196791, even if the liquid surface of the fuel within the fuel tank fluctuates due to vibration or the like applied to the fuel tank and an inlet of the breather pipe is instantaneously immersed in the fuel, the fuel is temporarily stored in the breather pipe, whereby the fuel is prevented from entering the breather pipe.
In this breather system, however, not only is the breather chamber required to be provided in the fuel tank apart from the fuel supply port, but also the breather pipe is extended to the outside going around the outer periphery of the fuel tank. Therefore, not only is the structure of the fuel tank itself complicated to increase the cost, but also handling of the breather pipe becomes difficult. Another problem is in a situation where the fuel tank with the breather chamber is placed on its lower side for an extended time. The immersion of the breather pipe in the fuel is thus also extended so that the fuel enters the breather pipe.